Javascript按照类似C语言printf进行格式化字符串

function fill(z, w, s) {
    w = parseInt(w || 0);
    s = String(s);
    z = String(z);
    let c = w - s.length;
    while (c > 0 && z.length) {
        s = String(z) + s;
        c--;
    }
    return s;
}

function format(fmt, ...args) {
    return fmt.replace(/%(0{0,1})(\d*)(\.{0,1})(\d*)([sdfj])/g, (match, z, w, d, p, s) => {
        let v;
        switch (s) {
            case 's': {
                let v = String(args.shift());
                v = fill(z || ' ', w || 0, v)
                return v
            }
            case 'd': {
                let v = Number(args.shift());
                v = fill(z || ' ', w, v)
                return v;
            }
            case 'f': {
                let v = Number(args.shift());
                if (p) {
                    v = v.toFixed(p);
                }
                v = String(v);
                if (w) {
                    let i = v.indexOf('.');
                    if (i >= 0) {
                        // 有小数
                        v = fill(z || ' ', w, v.substr(0, i)) + v.substr(i);
                    }
                    else {
                        v = fill(z || ' ', w, v);
                    }
                }
                return v;
            }
            case 'j': {
                let v = JSON.stringify(args.shift());
                return v;
            }
            default:
                return match;
        }
    });
}



console.log(format('The %7s %s cost %05d seconds. val=%04f v=%.3f', 'test', 'run', 10, 12.32, 0.13))
console.log('*************')

输出内容

The    test run cost 00010 seconds. val=0012.32 v=0.130
*************